Nicolaus Copernicus, Polish Mikołaj Kopernik
(born February 19, 1473, Toruń, Poland—died May 24, 1543, Frauenburg, East Prussia [now Frombork, Poland]), Polish astronomer who proposed that the planets have the Sun as the fixed point to which their motions are to be referred; that the Earth is a planet which, besides orbiting the Sun annually, also turns once daily on its own axis; and that very slow, long-term changes in the direction of this axis account for the precession of the equinoxes. This representation of the heavens is usually called the heliocentric, or “Sun-centred,” system—derived from the Greek helios, meaning “Sun.” Copernicus’s theory had important consequences for later thinkers of the scientific revolution, including such major figures as Galileo, Kepler, Descartes, and Newton. Copernicus probably hit upon his main idea sometime between 1508 and 1514, and during those years he wrote a manuscript usually called the Commentariolus (“Little Commentary”). However, the book that contains the final version of his theory, De revolutionibus orbium coelestium libri vi (“Six Books Concerning the Revolutions of the Heavenly Orbs”), did not appear in print until 1543, the year of his death.

Early life and education

Certain facts about Copernicus’s early life are well established, although a biography written by his ardent disciple Georg Joachim Rheticus (1514–74) is unfortunately lost. According to a later horoscope, Nicolaus Copernicus was born on February 19, 1473, in Toruń, a city in north-central Poland on the Vistula River south of the major Baltic seaport of Gdańsk. His father, Nicolaus, was a well-to-do merchant, and his mother, Barbara Watzenrode, also came from a leading merchant family. Nicolaus was the youngest of four children. After his father’s death, sometime between 1483 and 1485, his mother’s brother Lucas Watzenrode (1447–1512) took his nephew under his protection. Watzenrode, soon to be bishop of the chapter of Varmia (Warmia), saw to young Nicolaus’s education and his future career as a church canon.

Between 1491 and about 1494 Copernicus studied liberal arts—including astronomy and astrology—at the University of Cracow (Kraków). Like many students of his time, however, he left before completing his degree, resuming his studies in Italy at the University of Bologna, where his uncle had obtained a doctorate in canon law in 1473. The Bologna period (1496–1500) was short but significant. For a time Copernicus lived in the same house as the principal astronomer at the university, Domenico Maria de Novara (Latin: Domenicus Maria Novaria Ferrariensis; 1454–1504). Novara had the responsibility of issuing annual astrological prognostications for the city, forecasts that included all social groups but gave special attention to the fate of the Italian princes and their enemies. Copernicus, as is known from Rheticus, was “assistant and witness” to some of Novara’s observations, and his involvement with the production of the annual forecasts means that he was intimately familiar with the practice of astrology. Novara also probably introduced Copernicus to two important books that framed his future problematic as a student of the heavens: Epitoma in Almagestum Ptolemaei (“Epitome of Ptolemy’s Almagest”) by Johann Müller (also known as Regiomontanus, 1436–76) and Disputationes adversus astrologianm divinatricenm (“Disputations against Divinatory Astrology”) by Giovanni Pico della Mirandola (1463–94). The first provided a summary of the foundations of Ptolemy’s astronomy, with Regiomontanus’s corrections and critical expansions of certain important planetary models that might have been suggestive to Copernicus of directions leading to the heliocentric hypothesis. Pico’s Disputationes offered a devastating skeptical attack on the foundations of astrology that reverberated into the 17th century. Among Pico’s criticisms was the charge that, because astronomers disagreed about the order of the planets, astrologers could not be certain about the strengths of the powers issuing from the planets.

Only 27 recorded observations are known for Copernicus’s entire life (he undoubtedly made more than that), most of them concerning eclipses, alignments, and conjunctions of planets and stars. The first such known observation occurred on March 9, 1497, at Bologna. In De revolutionibus, book 4, chapter 27, Copernicus reported that he had seen the Moon eclipse “the brightest star in the eye of the Bull,” Alpha Tauri (Aldebaran). By the time he published this observation in 1543, he had made it the basis of a theoretical claim: that it confirmed exactly the size of the apparent lunar diameter. But in 1497 he was probably using it to assist in checking the new- and full-moon tables derived from the commonly used Alfonsine Tables and employed in Novara’s forecast for the year 1498.

Copernicus’s reputation outside local Polish circles as an astronomer of considerable ability is evident from the fact that in 1514 he was invited to offer his opinion at the church’s Fifth Lateran Council on the critical problem of the reform of the calendar. The civil calendar then in use was still the one produced under the reign of Julius Caesar, and, over the centuries, it had fallen seriously out of alignment with the actual positions of the Sun. This rendered the dates of crucial feast days, such as Easter, highly problematic. Whether Copernicus ever offered any views on how to reform the calendar is not known; in any event, he never attended any of the council’s sessions. The leading calendar reformer was Paul of Middelburg, bishop of Fossombrone. When Copernicus composed his dedication to De revolutionibus in 1542, he remarked that “mathematics is written for mathematicians.” Here he distinguished between those, like Paul, whose mathematical abilities were good enough to understand his work and others who had no such ability and for whom his work was not intended.

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